WASHINGTON — House of Representatives Speaker John Boehner said on Sunday he cannot imagine ever supporting gay marriage even though Senator Rob Portman, his friend and fellow Ohio Republican, very publicly reversed his opposition last week.

Portman became the most prominent Republican lawmaker to back same-sex marriage, doing so two years after his son told him he is gay.

“Rob is a great friend and a long-time ally,” Boehner, the top Republican in Congress, told ABC’s “This Week.”

“I believe that marriage is the union of one man and one woman. It’s what I grew up with. It’s what I believe. It’s what my church teaches me. And I can’t imagine that position would ever change,” added Boehner, who is a Roman Catholic.

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Portman served as U.S. trade representative and White House budget director under Republican President George W. Bush.

President Barack Obama last year announced his support for gay marriage. Nine of the 50 U.S. states and Washington, D.C. permit it. The Supreme Court is due to hear oral arguments this month in two gay marriage cases.

The Republican Party has become increasingly split on gay marriage, with some arguing that socially conservative positions such as opposition to same-sex marriage are contributing to the party’s election losses.

“We conservatives believe in personal liberty and minimal government interference in people’s lives,” Portman wrote in a newspaper opinion piece on Friday. “… One way to look at it is that gay couples’ desire to marry doesn’t amount to a threat but rather a tribute to marriage, and a potential source of renewed strength for the institution.”

On another contentious issue, Boehner declined to promise that the Republican-controlled House would hold a vote on any gun control measure passed by the Democratic-controlled Senate.

“If they pass something, I would make clear that we will review it,” Boehner said, stopping short of promising a vote.

Obama is seeking new measures to curb gun violence after the December massacre of 20 children and six adults by a gunman at a Connecticut elementary school. A Senate committee has approved four gun measures but their prospects in the full Senate are less clear.